Re: [PATCH v4 11/66] mm/mmap: Use maple tree for unmapped_area{_topdown}

[Vlastimil Babka]

On 12/1/21 15:29, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> 
> The maple tree code was added to find the unmapped area in a previous
> commit and was checked against what the rbtree returned, but the actual
> result was never used.  Start using the maple tree implementation and
> remove the rbtree code.

Nice cleanup. But...

> Add kernel documentation comment for these functions.
> 
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>

>  
>  	/* Adjust search length to account for worst case alignment overhead */
>  	length = info->length + info->align_mask;
>  	if (length < info->length)
>  		return -ENOMEM;
>  
> -	rcu_read_lock();
> -	mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
> -			   length);
> -	rcu_read_unlock();

Why is RCU locking being removed as part of this? Ditton in
unmapped_area_topdown()